The US and Russian nuclear arsenals could soon be unconstrained by any binding arms control agreements for the first time since 1972, triggering an expensive and dangerous new arms race, a group of former officials and experts from the US, Europe and Russia has warned.

In a statement to be published on Wednesday, the signatories point out that the 2010 New Start treaty limiting the deployed strategic warheads and delivery systems of the US and Russia, will expire in February 2021, unless urgent steps are taken to extend it.

Meanwhile, the Intermediate Nuclear Forces (INF) agreement is in danger of collapse, amid US accusations of Russian violations of the pact with the development of a new land-based cruise missile, and the Trump administration’s threat to develop a similar weapon in response.

Both Vladimir Putin, in recent statements, and Donald Trump, in his administration’s nuclear posture review, have declared plans to modernise and upgrade their arsenals involving new nuclear weapons capabilities.

The threatened return to an arms race between the world’s two biggest nuclear powers comes at a time of high tension in relations between Washington and Moscow, when US, Nato and Russian forces are operating in close proximity in eastern Europe and Syria.

“Without a positive decision to extend New Start, and if the INF Treaty comes to an end, there would be no legally-binding limits on the world’s two largest nuclear superpowers for the first time since 1972, and the risk of unconstrained US-Russian nuclear competition would grow,” the statement warned.

The statement is signed by former senior arms negotiators from the US and Russia, a former Russian chief of staff, Gen Victor Esin, former UK defence minister Des Browne and retired US senator Richard Lugar.

The US and Russia have stuck to the terms of New Start, which was signed eight years ago by their then presidents, Barack Obama and Dmitry Medvedev. It has been an exception to Donald Trump’s determination to erase his predecessor’s foreign policy record.

By the treaty’s deadline of February this year, both countries declared they had met its limits of 1,550 deployed strategic warheads, and 700 fielded delivery platforms such as intercontinental ballistic missiles (ICBMs), submarine-launched ballistic missiles and nuclear-capable bombers.

The US navy test-fires a nuclear-capable Trident II missile from the submerged submarine USS Tennessee in the Atlantic Ocean off the coast of Florida. Photograph: Phil Sandlin/AP

The treaty allows a five-year extension by mutual consent. Moscow has said it was open to discussion on the issue, and in an interview in March, Putin voiced interest in an extension or even possible further cuts in warhead numbers.

When he called to congratulate Putin on his re-election in March, Trump invited Putin to a summit “in the not too distant future to discuss the arms race, which is getting out of control”.

The Trump administration had put off any consideration of extending New Start until its nuclear posture review was complete and Russian met its treaty obligations by the February deadline. With those milestones reached, the top Pentagon official for nuclear and missile policy, Rob Soofer told the Senate on 11 April, “we’re going to begin a whole of government review of the pros and cons of extending that treaty.”

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Trump’s new national security adviser, John Bolton, has been a persistent critic of the INF treaty and New Start, which he has derided as “unilateral disarmament”. Republican hawks in the Senate, like Tom Cotton, have also declared their intention to pull the US out of the treaties.

Frictions over Russian meddling in western elections, the ongoing investigation into the Trump’s campaign’s possible collusion with those efforts in 2016, and Moscow’s military intervention in Ukraine and Syria, are all complicating the prospects of keeping a bilateral arms control regime in place.

Failure to agree on an extension in time could trigger a relatively rapid increase in arsenals, Daryl Kimball, the head of the Arms Control Association, said.

“Each side has significant ‘upload potential’. That means they have enough delivery systems and enough reserve nuclear warheads, to increase the number of deployed strategic warheads very rapidly, if they so choose,” Kimball said.